Low sulfur



AMA/rt United States Patent LOW SULFUR, MINERAL BASE LUBRICATING OILS AND METHODS FOR USING SAWIE No Drawing. Application September 8, 1953,

Serial No. 379,053

6 Claims. (Cl. 123-1) The present invention relates to improved lubricating oils for use in internal combustion gasoline engines of the recriprocating type. More particularly, the invention is concerned with improved automotive motor oils which are mineral-base lubricating oil compositions having, in comparison with prior art formulations, very low sulfur contents thereby reducing their tendency to contribute to an increase in the requirement of octane number of gasoline for a knock free operation of high compression ratio internal engines. The invention is especially concerned with lubricating oil compositions containing lowsulfur mineral oil base stocks and non-sulfur containing addition agents adapted to improve one or more characteristics of the composition. The invention is also concerned with methods for operating automotive engines having compression ratios of above about 7.0:1 with these improved lubricating oils in combination with essentially hydrocarbon mixtures, under conditions that result in a decrease of the formation of combustion chamber deposits of the type which contribute to octane requirement increase.

During recent years, the development and wide spread use of automobiles and other vehicles having relatively high compression ratio engines has focused attention to a problem of engine cleanliness that has serious economic implications. It has been consistently found by users of vehicles containing such engines, particularly, when they are run under mild driving conditions such as urban and suburban driving, that the engines knocked and lost power after relatively short operating periods. This difficulty occured even though detergent additive-containing lubricating oils and gasolines having high octane ratings meeting the automobile manufacturers recommendations were employed. Studies have shown that these difficulties occured when the combustion chambers of the high compression ratio engines contained films of resin-like deposits forming chiefly on the piston top, on valves, and on the under side of the cylinder head. The octane requirement to prevent knocking frequently increases by as much as 10 to 15 units during the first 3,000 to 5,000 miles of service and power losses as high as 10% are frequently observed.

A study of these deposits showed that the decrease in combustion chamber volume due to them, (and thus the increase in compression ratio) could account for only about 10 to 15% of the octane requirement increase observed. It was further found that the resin-like deposits were insulating in nature and decreased cooling through the combustion chamber walls. This results in heating up the incoming fuel charge and raises the overall combustion temperature, which in turn makes the engine more prone to knock. Thus the poor heat conductivity of the deposits accounts for the remaining octane requirement increase observed.

Chemical analyses have shown that the deposits in the organic portion generally contained carbon, hydrogen and oxygen in the atomic ratio of about :522 respectively, with small amounts of sulfur and nitrogen (0.5

to 4% by weight). Lead compounds, such as the oxides, chlorides, sulfates, etc., are also present in amounts as high as 50 to of the total deposits, when the gasoline contains tetraethyl lead (TEL) and halide scavengers for the TEL.

It has been found further that both the gasoline and the lubricant can be substantial contributors to the formation of combustion chamber deposits of the type that cause octane requirement increase (0R1). The mechanism of a particular component in forming such deposits is not known with certainty, but at least a substantial proportion of the resins appears to be closely associated with a tendency of a given component to form high molecular weight cross-linked resins at the hot flame conditions prevailing in combustion zones. This cross-linking phenomenon appears to derive from the property of the component itself as well as fromcatalytic effects caused by addition agents in the oil and fuel. This resin not only resisted combustion but also appears to have a binding effect in retaining carbon and inorganic substances in the deposits. Not only certain types of mineral oil components, but also additions agents improving the characteristics of the oil and certain components of the gasoline can contribute to formation of such harmful deposits.

It has been found in the past that the presence of substantial amounts of sulfur in the gasoline is deleterious to the effectiveness of tetraethyl lead for increasing the octane number of gasoline. It has therefore been preferred that leaded gasolines contain below about 0.20% by Weight, preferably about 0.10% by Weight, of said sulfur. More recent studies have shown that unexpected advantages in decrease ORI can be achieved by lowering the sulfur content of gasoline below the level at which the sulfur has any effect on the actual octane number of the gasoline containing tetraethyl lead. For minimizing ORI, it has been found important to decrease the sulfur content of leaded gasoline below about 0.02% and preferably below about 0.005% by weight. With such low-sulfur leaded fuels it has been found that combustion chamber deposits are formed, indeed; but these deposits are not of the type that contribute to CR1, and on the contrary they have catalytic anti-knock properties that seem to offset completely the physical pro-knocking effect of their thermal insulating properties and volume. If substantial sulfur is present in the fuel, however, lead sulfate and possibly other lead salts having pro-knock properties are formed in the combustion chamber leading to octane requirement increase. sulfur-lead interaction of some type takes place in the combustion Zone under combustion conditions that leads to the formation of harmful deposits.

It has been conventional practice to formulate motor oil compositions, particularly of the mineral oil base variety, that contain substantial amounts of sulfur, this sulfur being present not only in the mineral oil base stock, but also in the addition agents used to improve such characteristics as detergency, oxidation resistance, and the like of the finished composition. No particular attention has been given to reducing the sulfur content of such oils because the amount of such oil introduced into the combustion chamber was relatively small in comparison with the fuel, and therefore its effect in contributing to harmful sulfur deposits was negligible. It has been found however that this situation no longer obtains when using low sulfur fuels or fuels that, with the use of proper lead scavenging agents and the like, will not contribute to sulfur-containing deposits that have pro-knocking effects. Indeed, it has been found that the lubricating oil can contribute a substantial amount of potentially harmful sulfur during an engine operation with improved fuels. It is therefore a principal object It is evident that a 3 of the present invention to provide a lubricating oil composition of exceptionally low'sulfur'contentthat will-not in itself contribute to the formation of harmful sulfur deposits. it is a further object to teach a means for using this improved lubricating oil for lubricating the parts of a combustion chamber subject to friction in combination with an improved gasoline wherein neither the fuel nor lubricant will contribute substantially to harmful sulfur-containing deposits.

in accordance with the present invention, a lubricating oil composition is provided that comprises a lubricating oil base stock having a low sulfur content with at least one non-sulfur containing addition agent adapted to improve at least one characteristic of the finished composition. In a preferred embodiment of this invention, the total lubricating 'oil composition will have a sulfur content below about 0.1% by weight, preferably below 0.05% by weight. The lubricating oil base stock will comprise a major proportion of a low-sulfur mineral oil having lubricating characteristics, but more preferably the base stock consists completely of such a mineral oil. The non-sulfur containing additives dissolved in the finished composition will consist of one or more of those that improve such characteristics as viscosity index, detergency, resistance to oxidation or to the causing of bearing corrosion, pour point depressing, rust inhibition or other properties. A preferred composition will contain at least two ditferent types of additives conveying at least two characteristics. The 'best results are obtained with mineral oil-base compositions containing a minor portion of a mul'ti-acldit-ive system containing at least three different types of these or other additives that will form a finished oil having superior viscosity index, low pour point, more engine cleanliness and the like characteristics.

The lubricating oil components of the present invention are also preferably those types that do not contribute to CRT in the combustion chambers of the high compression ratio engines. These components preferably have relatively loW resinification indexes e. g, low tendency to form resin-like deposits during a combustion under a hot, smokeless flame such as a hydrogen flame. Mineral lubricating oil base stocks particularly adapted for this purpose are those that are substantially free of hydrocarbon components boiling above about 600 F. at a pressure of 10mm. Hg, such as bright stocks, residuums or heavier distillate components. A particularly suitable fraction is one that boils within the range of about 275 to 600 F. at this pressure and more preferably within the range of about 300 to 575 F. at this pressure.

A specifically preferred composition of the present invention is formulated with a major portion of a catalytic cycle oil, resulting from the catalytic cracking of gas oils and the like, which has been selectively treated for the removal of relatively more aromatic components and sulfur and which has been, if desired, dewaxed and/or clay treated. These refined catalytic fuel stocks have eX- tremely low sulfur contents, such as below about 0.05% by weight, and possess excellent stability and high viscosity index characteristics. If the proper boiling range is selected, they do not themselves contribute to the formation of resinous-like combustion chamber deposits. Treating methods other than catalytic cracking for producing mineral oils of low sulfur content are, however, contemplated in the present invention, although catalytic cracking is a particularly preferred method.

The non-sulfur additive system employed as a minor component of the oils .of the present invent-ion will be discussed in detail below. "Preferably, these additives comprise about 3 to 30% and preferably about to'25,% of the total oil composition.

The advantage to be obtained in the practice of the present invention in the operation of automotive engines is demonstrated in Table I, which shows a comparison of the amount of sulfur contributed by fuels and lubricants-in operations with-conventional fuels andlubricants, with low sulfur fuels and conventional lubricants, and with low sulfur fuels and the lubricants of the present invention.

TABLE I Sulfur contributed by lubricants vs. fuel in an average automobile [Oonsumptions assumed: 1 quart of oil per 1,000 miles, 13.0 miles per gallon of gasoline or 1.8# of oil and 469;? of gasoline/1,000 miles] .Pereeut of Lbs. of Sul- Sulfur fur Burned .Burned Per 1,000 Contrib- Miles uted by Lube Case A Present day 'Fuels and Lubes:

Fuel st'0.1%.Sultur O. 469 Oilat 0.5% Sulfur. 0. 009

Total 0.478 1.0

Case 8 Improved Fuel but Current Lube:

Fuelat 0.005% Sulfur 0. 024 Oilat 0.5% Sulfur 0.009

Total 0. 033 27. 0

Case C Improved Fuel and ImprovedLube:

Fuel at 0.005"? Sulfur 0. 0240 Oil at 0.05% t ulfur 0.0009

Total 0. 0249 3. 8

1 Fzels containing about 2 cc. TEL/gal. and conventional scavenging agen In Case A, it is seen that the conventional high sulfur lubricant will contribute .only about 3 of the total sulfur entering the combustion chamber of the average automobile. In Case B, however, the lubricant will contribute almost /3 of the total sulfur when using a low sulfur fuel. By using a combination of a low sulfur fuel (about 0;005'% '3) and the low sulfur lubricant of the present invention, the proportional contribution by the lubricant can be reduced to about or to levels equally as low as ,those now conventional with high-sulfur lubricants and high-sulfur fuels.

Therefore, this invention also contemplates the improved results to be obtained in operating automotive engines with the low-sulfur lubricants of the present invention in combination with low-sulfur, leaded fuels. The invention also contemplates operations with the oils of the present invention in combination with high-sulfur leaded "fuels containing high boiling lead scavenging agents, such as various aromatic halides and the like to be defined more fully herein, whereby the harmful suifur-like deposits are not formed in substantial amounts in the combustion chamber.

Various methods for preparing and formulating lubricating oil compositions of the present invention and of employing them as lubricants in automotive engines and the like are presented in the following examples. it is to be understood that these examples are given as illustrations of the present invention ;and are not to be construed as limiting the scope thereof in any way.

Example [Per -reparation of mineral lubricating oil base stocks Mineral oil base stocks were prepared by catalytically cracking .gas oils and recovering a'cycle oil boiling above the heating oil range 'inaccordance with a procedure disclosed and claimed in 'U. S. Serial No. 187,709 filed September 30, 1950 in the name of Forrest H. Blandiug. This patent issued on November'24, 1953, as Patent No. 2,660,552. In one series of operations, gas oil distillates from various types of crudes including Mid-Continent crudes was subjected to fluid catalytic cracking, employ ing a silica-alumina type catalyst under conventional cracking conditions. The refractory cycle oil produced in this catalytic cracking operation, the cycle oil conphenol extracted to obtain a 34 volume percent rafiinate which was then dewaxed and clay contacted under conventional conditions to obtain a finished lubricating oil cycle stock representing 25 volume percent of the original sisting of hydrocarbon components resistant to further cycle oil.- degradation under the conditions employed, was segre- For comparative purposes, a lubricating oil distillate gated and selectively extracted with phenol solvent using from a Middle East crude was solvent extracted and approximately at 204 volume per cent treatment, based dewaxed. Inspections and tests on the various base on the feed stock, and an extraction temperature of about stocks are shown in Table III below: 140 to 157 F. A 50% solvent raffinate yield was ob- TABLE III tained. The solvent raffinate was then dewaxed to obtain a yield of 80 volume percent of dewaxed oil, based Lube-9 made f Middle 'fip Crude on the stripped rafiinate, the dewaxed rafiinate having a pour point of about +25 F. The dewaxed raffinate F G H :r was then distilled to obtain an initial to 27% overhead fraction. Cycle Stock:

For comparative purposes, a lubricating oil distillate Base Smck Inspectmns gggi g C 1 Y0 6 obtained from the same type of Mid-Continent crude Dewaxed from Stock was solvent extracted with phenol anddewaxed under 3 555%? gfiig Extract conventional conditions to obtain a distillate fraction finate having approximately the same gravity, boiling range and viscosity characteristics as the 0 to 27%extractedand Gravity,.%PI-.-- 10.7 37.2 32.8 0 dewaxed cycle oil. The refined distillate is designated as 23:; 23:3 a solvent neutral. Both the 0 to 27% fraction and the Viscosity Index 52 135 114 solvent neutral boiled below 600 F. in an ASTM Engler- Pour, a F +80 +25 +15 (1) type distillation at10mm.pressureHg. glag g k n un 365 3351 at (1) Various physical inspections and analysis were obtained 53 3%, g ggggg 34 A 0 on the various feeds and extracts. Comparative data son 20% 8% are Shown in Table H below- Neutralization No., rugs. KOH/ TABLE 11 critters-sausages:stars: 113% 3:3 :82 S3 Sulfur, Wt. percent 3.52 0.01 0.27 5.3 Premzum lubes made from various crude: Sign, mgs. Sludge/10 gins. (24 1 A B O D E Aromatics, Wt. percent 64 4 13 83 Cycle stock 1 Not determined. Base Stock Inspections ggglg Egg; It is noted that Base Stock G, the extractedand dewa gv a xed 0 t 2 ew d g waxed cycle oil, had an exceptionally high viscosity index g a a X ac of 135, an exceptionally low sulfur content of 01% and Raff- 4 excellent stability as measured by the Sligh test.

Gravity CAP]. M8 32. 4 34.3 as Example 2. -Engine performance characteristics of cycle Vise.@100 F., SSU.. 152 81 74.7 oil-base lubricating ozl compositions ViSo.@210F.,SSU 45.4 43.8 37.6 37.0 Viscosity Inde); 110 104 101 A blend containing approximately 90 Weight percent P0111301. u 90 +25 +20 +5 I of Base Stoch C andlO weight percent of a viscosity P p---- 365 355 340 (3) index improving additive was prepared. The V. 1. imggfig figf fig itgfijg A 20% O prover consisted of about 25% by weight of polyiso- KOH/gm .01 .03 .01 butylene having a Staudinger average molecular weight oonmdson Carbon Wt of about 15,000 and 75% by weight of a mineral oil Percent 3.3 .04 .01 .01 base Stock fifigflfg mggi ifi y This blend was tested in a Lauson single cylinder ens. f 619 0) 87 gine having a 6.5 :1 compression ratio head. The engine Aromatics'whpercent 48 6 O O was loaded with an induction motor at 1840 R. P. M. lNot determined and 10.5 brake kilowatt load for a period in the range of about 120 to 200 hours using a spark advance of 12 Base Stock A, the feed to the solvent extraction unit, BTDC. These operating conditions have been found to had a sulfur content of 0.87%. Solvent extraction procorrelate with full scale field tests of automobiles having duccd Base Stoc s B and C having ex rem y low Sulfur 7.5:1 compression ratio engines with respect to octane contents of about 0.04%. Note that the su fur Conte requirement increase. In these tests the engine was operof the phenol extract was (column Showing ated with a hydrocarbon fuel that itself did not contribute that the predominant portion of the sulfur compounds t ORI, is concentrated in the material removed by solvent ex- Th ults of th se tests are shown in Table IV below: traction. In contrast, the typical commercial dewaxed TABLE IV ratfinate, Solvent Neutral oil (column D), had a sulfur content approximately 10 times that of the refined cycle Octane requirement increase in Lauson engine oils. This Solvent Neutral is made from virgin lubricant distillates rather than cracked cycle stock. It is also Octane Requirement noted that the oxidation stability of the refined cycle oils, I ubrwmt as measured by the conventional Sligh test, was ex- J Initial Equiceptionally better than that of the virgin Solvent Neutral. The viscosity indexes of the refined cycle oils were also quite high Refined Cycle Stock +10% Polybntene 6O 61 Another operation was carried out in which a gas oil obtained from a mixture of Middle East crude was cata- It is seen that the blend of refined cycle stock and lytically cracked and cycle stock recovered therefrom was polybutcne additive, which blend contained less than 0.05

weight percent sulfur, did not contribute to any appreciable extenttoORL The mineral oil base stocks used in the practice of the present inventionmay beobtained from various types of crudes such as those of parafiinic, naphthenic or mixed base components. Mid-Continent type crudes are useful as well as-those ofthe MiddleEastern type, Texas Coastals and the like. The lubricating oil components of these crudes should be refined in order to reduce sulfur contents to the low levels required .to obtain the benefits of. the present invention. Such refining procedures include catalytic cracking, hydro'fining, ztreatment with finely divided sodium in the presence of alcohols, ethers, ketones and the like, formaldehyde .treatment, treatment with mineral acids, and the like. ti-onal treating procedures such as acid treatment and the like will not be effective .for obtaining extremely low sulfurlevels, and acombination of treating procedures will usually be required to obtain the desired results. Such combinations of treating procedures may include catalytic cracking to obtain :highly stable cycle stocks of the type discussed above, following which the relatively more aromatic components are removed by selective adsorption or extraction with silica gel or various solvents such as phenol cresylic acids, liquid S02 furfural or the like. Catalytically hydrogenated lubricating oil distillates may likewise .be subjected to additional refining steps to reduce sulfur content further and to improve other characteristics of the oils. The mineral oil base stocks may also be subjected to such treating procedures as dewaxing, clay treating and the like. These stocks preferably contain below about 'by weight ofaromatic rings and have a ratio of aromatic rings to naphzthenic rings of below about 0.3.

It is also preferred that the base .stock be distilled to exclude relatively high boiling mineral .oil components, particularly those boiling above about 600 F. at a pressure of 10 mm. Hg; more preferably the base stock will boil below about 575 F. at this pressure in the simple distillation test of the so-called vacuum Engler type.

Although bright stock, or residuum components may be employed in the practice of the present invention provided their sulfur content is sufficiently low, it is preferred to exclude such residual components particularly if the base stock is to be substantially non-contributing to ORI. it is generally desired that a low sulfur-mineral .oil base stock be themajorportion of the lubricating oil base stock, and preferably constitute all of the base stock.

However minor amounts of other lubricating oil base stocks and blending agents include hydrogenated oils,

synthetic oils such as polymerized olefins, synthesis products from the reaction of oxides of carbon with hydrogen, hydrogenated coals, shale oil derivatives, synthetic polyester and polyether type lubricating oils, and the like.

The .base stock preferably has a viscosity index above about 100 and has a Saybolt Universal (SU'S) viscosity at 100 F. in the range of about 50 to 160, and at 210 F. to about 33 to 50. As mentioned heretofore, the base stock should have a. sulfur content below about 0.10 Weight percent, preferably below 0.05 weight percent sulfur.

The non-sulfur containing additives useful in the practice of the present invention may be selected from a variety of materials that have characteristic improving properties without contributing to sulfur increase.

It is generally desired to add .a viscosity index improver. High molecular weight hydrocarbon V. I. improvers such as the polymerized lower olefins (i. e., polymerized C3-C5 oletins) are quite effective. For example, polymerized hutenes, such as polymerized iso butylene having a molecular weight in the range of about 5,000 to 50,000, preferably about 10,000 to 25,000, are quite useful. These polymerized olefins are readily prepared by procedures'well known-to the art.

Other V. I. improvers include the polymethacrylate As a general rule convenesters, fumarate-vinyl .acetate copolymers, polyalkyl styrenes,-.and thelike. The viscosity index improver may be .used .in'amounts in .the.range of about0.5 to 30% by Weight, ,preferably about 1 .to 10% by Weight, based on the finished lubricating oil. In producing a finished lubricant having a low PORK, it is preferred that the V. I. improver be of the non-contributing type. The high molecular weight olefins .such as the polyisobutylenes .are particularlyadvantageous in this respect. However, mixtures of various types of V. I. improvers may be used.

Detergency improving additives may be selected from a-largegroupof materials, particularly the metal containing. materials that aretuseful in this respect. Certain types of .ashlessl-syntheticdetergent additives however are also useful. Such :detergenhadditives include metal salts and soaps such as metal naphtenates, including zinc soaps of petroleum .naphthenic .acids, particularly soaps obtained from naphthenicacids havingmo'lecular weights of about .-to 400, metal phenates such as the alkali metal, alkaline earth .metal and heavy metal phenates. Such compounds include calcium decyl phenate, barium text.- octyl-phenol, metal bis phenols and the like.

Specific alkyl phenols from which such detergents can be made include the xylenols, thyniol, decyl phenols and other long=chain "alkyl substituted phenols, wax phenols, petroleum phenols recovered from distillate petroleum oils, and particularly tertiary aliphatic substituted phenols :such as tertl-amyl phenol, tort-octyl phenol and the like may be used. Bis phenols such as 2,2-bis- (2-hydroxy-3-tert.-butyl.=5 methylphenol) propane, 2,2- methylene bis (4methyl-6-tert. butyl phenol) and the like may ilikewise rbe employed. Various amino phenols and-their substitutedderivatives such as alkyl para amino phenols and the like may also be used. It is also to be understood .that .these ,phenols may be used as such for improving oxidation characteristics.

Other suitable detergent additives include metal phosphates and metal phosphites, high molecular weight polymetha'crylate-type esters which :may be used as ashless detergents and thelike. The detergent additives may be present in amounts from as lowas about 0.5% up to about 10% by weight or even higher, based on the total composition, althoughan amount in the range of about 2 :to 38% are generally effective. It is generally preferred that the detergent inhibitor, as in the case of the V. l. improver, contribute very little to ORI.

The phenols and phenolic type compounds mentioned above may also be used per so as antioxidants. Other types of nonsulfur containing materials may however be employed as anti-oxidants and bearing corrosion inhibitors. As a general rule in the range of about 0.1 to 5% by weight, .based on the total lubricating composition, of these compounds will be sufficient to improve these characteristics of the lubricating oil.

A small amount of a pour depressant additive may also be incorporated in the finished composition in order to obtain improved pour-point stability and decreased pour ipoint. .Suchpourdepressants include condensation products of chlorinated waxy naphthalene or phenol, various polymers (and coepolymers of unsaturated esters and the like. For example, .a .co-polymer of the furnaric acid esters of coconut :oils :and of vinyl acetate in a 10/20 weight ratio :is an extremely effective pour depressant when used in relatively small concentrations. In the range of about'0.0l to 5% by weight of such materials will :usually be adequate.

.Other additives that may be used in the lubricating oil composition include anti-rust agents such as the partial esters of polyhydroxy compounds including the oleate of ,sorbitan polyglycol, acid phosphates, and the like; dyes, oiliness agents, assisting agents such as the higher alcohols including octyl alcohol, lauryl alcohol, and .stearyl alcohol, extreme pressure agents, etc.

.As mentioned .heretofore, the finished lubricating oil composition may contain one orimore of the above types Amount,

Component Volume Percent Base Stock (Example 1) 35 Polyisobutene V. I. Improver (Example 2) 8 Chlorinated Wax-Naphthelene Pour Depressant... 2 Barium Cetyl Phenate Detergent 4. 1,6-Ditertiary Butyl-4-Methyl Phenol (Antioxidant) 0. 5

This blend has a sulfur content below about 0.04%.

The gasolines used in high compression engines and the like with the oils of the present invention may be any suitable high octane, essentially hydrocarbon gasoline such as those having ASTM research octane numbers in the range of about 75 to 100. Hydrocarbon components that may be used in formulating such gasolines include straight run distillates from various types of crudes, alkylates, high octane polymers of low molecular weight olefins, hydroformates, reformed gasoline fractions sch as platformed gasolines, catalytically cracked naphthas and the like. Such gasolines are usually formulated by mixing 2 or more of the above general types of components to form fuels meeting octane requirement, vapor pressure, stability, and other specifications.

In order to form finished gasolines containing below about 0.02% by weight, preferably below 0.005% by weight, of sulfur, some or all of the various components that go into the gasoline will usually have to be treated for sulfur reduction. Such treating procedures include prompt caustic washing of the sulfur-containing material in the absence of oxygen soon after a catalytic cracking operation, hydrofining of cracked naphthas, treatment of naphthas with finely divided sodium in the presence of oxygen-containing organic compounds such as alcohols or ethers, and the like.

The amount of tetra-ethyl lead used in such gasolines will generally range from about 0.5 to 3 ccs. per gallon. The TEL fluid will also contain a lead scavenging agent such as ethylene chloride, ethylene bromide and the like. These amounts of TEL will be sutficient to increase octane numbers to high levels under ordinary conditions.

The advantages of the present invention may also be obtained by operating an engine with the improved oil using a sulfur-containing fuel, such as one having above 0.1 weight percent sulfur, containing a lead scavenging agent that is relatively high boiling and stable. The higher boiling agents are more suitable than the conventional ethylene halides, for example, for effecting complete removal of the lead from the combustion chamber or for forming deposits that do not have a pro-knock effect. The higher boiling scavenging agents are those having substantially the volatility characteristics of tetraethyl lead. These materials include halogenated aliphatic hydrocarbons such as hexa chloro-butadiene, and halogenated alkyl aromatics such as bromo xylenes, including mixed dibromoxylenes; dibromo toluenes, 3,4 dichlorocumene; 1,2 dibromobenzene; 1,2,4- trichlorobenzene; 2,4 dichlorotoluene, their mixtures and the like. Preferably these compounds have vapor pressures at F. of about 0.5 to 5.0 mm. Hg. In excess of about 0.5, preferably above about 1.0 stoichiornetrical equivalents of these agents, based on the TEL, may be added to the fuel. These higher boiling scavenging agents are taught in U. S. patents such as 2,496,983; 2,574,321; 2,479,900; etc.

It will be obvious that the gasoline fuels used in the practice of the present invention may also contain other addition agents such as anti-oxidants, gum inhibitors; solvent oils, rust inhibitors; metal deactivators and the like.

What is claimed is:

1. In the operation of an internal combustion engine of the reciprocating type having a compression ratio above about 7:1 in which an essentially hydrocarbon tetraethyl lead-containing fuel composition is introduced into the combustion chamber thereof under combustion condidone, the improvement for reducing the formation in said combustion chamber of sulphur-containing deposits of the type that increase the fuel octane requirement of the engine, which comprises lubricating the parts of said combustion chamber subject to friction With a lubricating oil having a decreased tendency to contribute towards octane requirement increase in said engine, said lubricating oil consisting essentially of a major portion of a mineral oil base stock which is a solvent extracted and dewaxed catalytic cycle oil distillate boiling within the range of about 300 to 600 F. at an absolute pressure of about 10 mm. Hg and a minor portion of at least one non-sulfur addition agent sufficient in amount to improve at least one characteristic of said composition, said lubricating oil having a total sulfur content not substantially above about 0.1 weight percent.

2. The method defined by claim 1 wherein said fuel contains less than about 0.02 weight percent sulfur.

3. The method defined by claim 1 wherein said fuel contains a relatively high boiling lead scavenging agent characterized by having volatility characteristics similar to those of said tetraethyl lead.

4. The method defined by claim 1 wherein said fuel contains less than about 0.005 weight percent sulfur.

5. The method defined by claim 1 wherein said fuel contains a halogenated aromatic lead scavenging agent having a vapor pressure within the range of about 0.5 to 5 mm. Hg at 120 F.

6. The method defined by claim 1, wherein said lubrieating oil has a total sulfur content below 0.05% by weight.

References Cited in the file of this patent UNITED STATES PATENTS Blanding Nov. 24, 1953 OTHER REFERENCES 

1. IN THE OPERATION OF AN INTERNAL COMBUSTION ENGINE OF THE RECIPROCATING TYPE HAVING A COMPRESSION RATIO ABOVE ABOUT 7:1 IN WHICH AN ESSENTIALLY HYDROCARBON TETRAETHYL LEAD-CONTAINING FUEL COMPOSITION IS INTRODUCED INTO THE COMBUSTION CHAMBER THEREOF UNDER COMBUSTION CONDITIONS, THE IMPROVEMENT FOR REDUCING THE FORMATION IN SAID COMBUSTION CHAMBER OF SULPHUR-CONTAINING DEPOSITS OF THE TYPE THAT INCREASE THE FUEL OCATANE REQUIREMENT OF THE ENGINE, WHICH COMPRISES LUBRICATING THE PARTS OF SAID COMBUSTION CHAMBER SUBJECT TO FRICTION WITH A LUBRICATING OIL HAVING A DECREASED TENDENCY TO CONTRIBUTE TOWARDS OCTANE REQUIREMENT INCREASE IN SAID ENGINE, SAID LUBRICATING OIL CONSISTING ESSENTIALLY OF A MAJOR PORTION OF A MINERAL OIL BASE STOCK WHICH IS A SOLVENT EXTRACTED AND SEWAXED CATALYTIC CYCLE OIL DISTILLATE BOILING WITHIN THE RANGE OF ABOUT 300* TO 600*F. ST AN ABSOLUTE PRESSURE OF ABOUT 10 MM. HG AND A MINOR PORTION OF AT LEAST ONE NON-SULFUR ADDITION AGENT SUFFICIENT IN AMOUNT TO IMPROVE AT LEAST ONE CHARACTERISTIC OF SAID COMPOSITION, SAID LUBRICATING OIL HAVING A TOTAL SULFUR CONTENT NOT SUBSTANTIALLY ABOVE ABOUT 0.1 WEIGHT PERCENT. 